The present invention relates to a method and circuit for preventing batteries from swelling.
Lithium Sulfur (LiS) rechargeable batteries provide users with high-energy and light-weight solutions. For example, LiS batteries developed by Sion Power™ Corporation, Tucson Ariz., are reported to be capable of delivering a specific energy of 400 Wh/kg and an energy density of 425 Wh/liter. The specific energy of the LiS battery exceeds that of state-of-the-art Lithium Ion chemistry by a factor of greater than two, while the energy density stands at an equivalent level. That is, a LiS battery provides the same runtime for a portable computer in less than half the weight, or twice the runtime in the same weight while having a volume comparable to a Lithium Ion battery. Another reported advantage of LiS batteries is their ability to work well in very cold weather. Typical applications include unmanned aerial vehicles, military communication systems, rugged notebook computers, tablet personal computers, and portable medical devices.
Recently, there have been numerous reports claiming battery swelling in certain types of notebook/laptop computers. In mild case, batteries swell but remain functional. In these cases, keyboard and/or trackpad functionality is affected by the rising of internal components. In severe cases, the swelling is striking enough to bulge the bottom of the notebook/laptop case, and sudden shutdowns are experienced due to non-functional batteries. Battery swelling is typically the final stage before explosion. Some reports address extreme cases wherein batteries caught fire with explosive force. According to one report, the laptop computer was charging at the time of fire but not in use (asleep with the lid shut). Generally, these are Lithium Ion (Li Ion) batteries, and the cause of swelling is considered to be overheating. Due to such safety problems associated with certain types of Li Ion batteries, some computer manufacturers are now opted for Lithium Polymer (Li Po) batteries: one of the supposed advantages of Li Po batteries is reduced combustibility.
In the appended figures, similar components and/or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a dash and a second label that distinguishes among the similar components. If the notation “-m” is used for the second reference label in the specification, the description is applicable to any one of the components having the same first reference label with different second labels 1 through n, where 1≦m≦n.